This application claims the priority of 198 04 462.3-12, filed Feb. 5, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a chain tensioning arrangement for an internal-combustion engine. More particularly, the present invention is directed to a chain tensioning device arranged in a timing case and acting on a timing chain that is driven by a crankshaft in an internal combustion engine.
A chain tensioning arrangement is shown in German Patent Document DE 40 17 601 C2. This chain tensioning arrangement exercises a tensioning force onto a timing chain. The camshaft of the internal-combustion engine is drivably connected with the crankshaft by the timing chain. The chain tensioning arrangement, which is to be operated hydraulically, acts upon a movable chain guide. The chain guide is in sliding contact with the timing chain so that the tensioning force generated by the chain tensioning arrangement is transmitted by way of the chain guide to the timing chain. The chain tensioning arrangement is fastened to a timing case in which the timing chain is accommodated. When the chain is worn, the chain tensioning arrangement provides a defined tensioning of the timing chain.
Because of the control elements and supply lines of the chain tensioner, this arrangement has a complicated construction and is therefore correspondingly susceptible to disturbances and is maintenance-intensive. Particularly for mounting and demounting, diverse connections must be connected with one another. In addition, an oil pump is required for providing the hydraulic pressure.
A different, purely mechanically operating chain tensioner is shown in German Patent Document DE 39 41 903 C2. The chain tensioner contains a tensioning member which is movably disposed in a housing and is acted upon by a spring in the direction of the timing chain. For mounting of the chain tensioner, the tensioning member can be locked by means of a locking pin. The locking pin extends through the chain tensioner housing so that the tensioning member does not act upon the timing chain and an easy mounting is possible. After the chain tensioner is inserted into the case of the internal-combustion engine, the locking pin is removed and the chain tensioner takes up its tensioning position acting upon the timing chain.
In the case of this chain tensioner, there is the risk that after mounting, the locking pin accidentally may not be removed so that the tensioning member remains in its mounted position and the timing chain is not tensioned. If this omission is not noticed, the untensioned timing chain may damage the engine by beating and skipping. If the omission is not noticed until after the conclusion of the assembly of the internal-combustion engine, the timing case must be removed at considerable additional expenditures and the locking pin must be released, which results in additional costs.
The present invention is directed to overcoming these problems by providing a chain tensioning arrangement comprising a simple device with respect to its mounting and operational reliability.
According to the present invention, the problems of the prior devices are solved by means of a chain tensioning device being mounted in a timing case in an internal combustion engine. The tensioning device comprises a tensioning member which is clamped by a releasable locking pin which extends below the floor of the timing case.
The length of the locking pin is dimensioned such that a section of the pin protrudes out of the timing case. As such, during final assembly while the locking pin is inserted, i.e., when a tensioning member is locked in the mounted position, it is impossible to leave the locking pin in place because the oil pan, which covers the timing case, cannot be mounted. The free end of the locking pin projects downward beyond the floor of the timing case. The oil pan cannot be mounted before the locking pin is removed and the tensioning member can take up its tensioning position. As such, the locking pin cannot be mistakenly left in the timing case.
The downward-projecting locking pin also has the advantage that, in the area of the timing case, no additional components are required for mounting the chain tensioning arrangement. Such additional components, in addition to increasing the variety of parts, can result in a weakening of the housing and in problems with the tightness. In particular, it is not necessary to provide a lid in the timing case receiving the chain tensioner in order to be able to withdraw the pin after the installation of the chain tensioner though the opened lid.
In an expedient embodiment, the locking pin has an operating grip which, in the mounted position, is situated outside the floor of the timing case. This facilitates the gripping and operating of the pin and excludes a mounting of the oil pain in the event that the locking pin is accidentally still inserted. The size of the operating grip increases its visibility, so that the fitter's attention is drawn to the locking pin still situated in the timing case.
Viewed in the axial direction of the locking pin, the operating grip is preferably longer than the depth, measured in the same direction of the oil pain. This ensures that the oil pan can definitely not be mounted while the pin is inserted. The locking pin may be manufactured of a wire-formed part which is easy to process and from which, particularly at low expenditures, an operating grip can be formed which is constructed in one piece with the pin body.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.